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Beginning the Structural Work

Part 9 of Conserving a Canaletto

January 30, 2013 by James Squires

It’s now time to move onto the structural phase of the conservation treatment for the Canaletto work. Structural work entails further securing of any loose media, such as paint or ground, and any repairs if necessary to the canvas and stretcher. Our Canaletto was lined in the past, which means that the original canvas was adhered to a secondary canvas. There are a variety of reasons historically why paintings were lined, but in the case of the Canaletto it was most likely due to the tear in the original canvas. Without lining, there are very few effective ways to regain overall planarity, or flatness, of the original canvas.

Fortunately the ground and paint layers remain well-adhered to the original canvas. However, the degraded glue/paste adhesive used to line the original canvas to the secondary canvas has imparted a visually distracting texture to the paint surface, which in turn de-emphasizes the artist’s brush work.

To resolve the problem, I will be separating the two canvases, and using some unique conservation tools and equipment to remove the distortions.

Before actual separation of the two canvases, I have to first protect the paint surface by applying a Japanese tissue facing to it with a starch-based adhesive. The tissue ensures that if any paint is dislodged during canvas separation process, it will be held in place so that I can go back in and re-adhere it to the original canvas as necessary.

As a result of its aging characteristics, the glue/paste lining adhesive has degraded, and the bond already was weakened. I was able to gently and carefully slide a thin spatula-like tool between the two canvases to further break the adhesive bond and facilitate separation.

Once separated, I mechanically removed the residual adhesive on the reverse of the original canvas with an aqueous gel solution and scalpel.

Conservation is the study of artists' materials and how they age. As a result of aging and prior interventions, it is not unusual for paintings on canvas to exhibit changes in the form of distortions. The planar distortions in this canvas were caused by the lining adhesive. In order to reduce them, I take into consideration the inherent characteristics of canvas. Canvas, like wood and paper, is hygroscopic—its size and shape change with respect to the amount of moisture absorbed by the yarns. I take advantage of these properties to remove/reduce the distortions by introducing moisture and heat in a very controlled way to first relax the yarns, then flatten them. This is achieved by using a piece of equipment called a vacuum hot table.

Next I will complete the structural phase of treatment and prepare the picture for the final phase—restoration.

This post is one in a multi-part series by Denver Art Museum staff on a long lost painting located in our collections. Find links to more from the series.

I was happy to hear from Timothy Standring, the curator of European painting and sculpture, that the Denver Art Museum was awarded the TEFAF grant to treat a long lost Canaletto picture, Venice: the Molo from the Bacino di San Marco.

My story is about the discovery and subsequent process of reaching consensus on the attribution of an unpublished early work by the Italian veduto (vista or views) painter Giovanni Antonio Canal, called il Canaletto I 1697 – 1768 at the Denver Art Museum.

I’ve finally been able to more closely examine the Canaletto to gain a better understanding of its present overall condition and treatment history. Generally, the picture is in better shape than I anticipated. To come to that conclusion I used a variety of evaluative and analytical techniques to assess the painting’s structural and aesthetic state.

In this post I will review (with pictures!) my findings. The techniques discussed were: normal, raking and specular illumination, ultraviolet-A radiation, and x-radiation. I was able to gather useful information from all of the techniques for my assessment.

After many hours and consultations with Timothy, cleaning is complete. I am always amazed at how much more one sees of a picture once the discolored varnish is removed—subtle details in the composition become visible and the picture's overall sense of depth is enhanced.

It’s now time to move onto the structural phase of the conservation treatment for the Canaletto work. Structural work entails further securing of any loose media, such as paint or ground, and any repairs if necessary to the canvas and stretcher.

The idea of reversibility is a very important concept in modern conservation practice. I chose materials with good and known aging characteristics, understanding that my work may need to be removed and/or redone, in the future. It is important that my conservation treatments are reversible.